Agriculture Reference
In-Depth Information
environments and the microbiology of foods is recognized (al-Dagal and Fung 1990),
and lateral transmission by the airborne route has been demonstrated in animal produc-
tion (Holt and others 1998). In contrast, the role of air in the dissemination of human
pathogens in agricultural environments remains undefi ned. It is currently diffi cult to
predict the associated health risks due to a lack of information on the fate and transport
of bioaerosols or contaminated dusts in open environments (Pillai and Ricke 2002).
Given the frequent association between proximity to potential sources of fecal con-
tamination and produce-associated outbreaks, there is a manifest need to determine
the risk of airborne transmission in horticultural production systems.
Contamination at Harvest
Harvest provides many opportunities for the introduction to or dissemination of human
pathogens in fruit crops. Fruit destined for the fresh market is generally picked by
hand. The role of hands in the transmission of human pathogens during food handling
or food preparation is well established (Bidawid and others 2000; Courtenay and
others 2005). Prevention strategies based on physical barriers such as gloves or dis-
infection using soaps and sanitizers can effectively reduce such risks in the food-
processing or food-service environment (Kramer and others 2002; Montville and
others 2002; Michaels and others 2003, 2004). Although there is evidence that the
hands of fi eld workers can become contaminated with human pathogens during harvest
(Materon and others 2007), little is known about their role in the transfer of contami-
nants to fruit. In addition, sanitation schemes designed for food handlers may not be
adaptable to the agricultural environment where constant soiling of hands and contact
with potential sources of contamination are unavoidable. In some cases the wearing
of gloves may be too restrictive to permit effi cient harvest.
Contact between fruit or with surfaces in bins or conveying equipment increases
throughout harvest. Research carried out with melons (Gagliardi and others 2003),
apples (Abadias and others 2006) and persimmons (Izumi and others 2008) indicates
that such contact results in higher microbial loads on the external surfaces of fruit,
and that soil is likely the main source of microorganisms acquired at this stage. In
some cases water may be used to convey, wash, or cool fruit in the fi eld. The micro-
biological quality of water used in these operations can be maintained by the use of
a sanitizer. Chlorine is widely used for this purpose, although chlorine demand tends
to increase rapidly in fi eld units due to soil or detritus accumulation, and effective
antimicrobial levels can be diffi cult to maintain.
A Case Study: Dissemination of Enteric Bacteria in
Sweet Cherry Orchards
Considerable research has been carried out to identify sources of human pathogens,
the means by which they are disseminated, and their fate in vegetable production
systems. Comparatively less effort has been directed at understanding these occur-
rences in fruit production systems. Evidently, most fruit-bearing plants are diffi cult to
grow in the laboratory, and biosafety issues prohibit fi eld inoculation with actual
human pathogens. Hence different approaches are needed to establish the behavior of
human pathogens in fruit production systems. The bacterium
E. coli
has long been
